You have fused information about three different men named William Brightwell into one.To clarify:
1)William Brightwell (1779-1831),son of Reynold Brightwell & Drucilla Allmand NEVER left Prince Edward Co VA.He is very well documented in census, deeds & tax records.
2) A DIFFERENT William Brightwell (b.1765-1775) was living in Barnwell/Edgefield Co SC by 1800.I definitely believe that he was the son of Reynold Brightwell (d.1781 Granvill Co NC) & wife Mary ________ (living 1810 Edgefield Co SC). This William appears to have died in South Carolina although several of his children settled in south Georgia.
Neither of the two men listed above was old enough to be a Revolutionary War soldier.The war ENDED in 1781.
3)William Brightwell (whose siblings Anderson Brightwell & Lucy Powers, received the bounty land (NOT PENSION) that William was entitled to for Revolutionary Service) lived, DIDNT MARRY and died in King William Co VA